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https://issues.apache.org/jira/browse/HDFS-385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12727855#action_12727855
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Hong Tang commented on HDFS-385:
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Some minor nits:
- In class BlockPlacementPolicy, the javadoc for chooseTarget contains an
unused parameter excludedNodes.
- There are two versions of abstract chooseTarget(), is it possible to provide
a default implementation for chooseTarget(FSInodeName srcInode, int
numOfReplicas, DatanodeDescriptor writer, List<DatanodeDescriptor>
chosenNodes, long blocksize) on top of chooseTarget(String srcPath, int
numOfReplicas, DatanodeDescriptor writer, List<DatanodeDescriptor>
chosenNodes, long blocksize) ?
- There is asymmetry for chooseTarget which takes a list of DatanodeDescriptor
and returns an array of DatanodeDescriptor. Why not returning a List too?
> Design a pluggable interface to place replicas of blocks in HDFS
> ----------------------------------------------------------------
>
> Key: HDFS-385
> URL: https://issues.apache.org/jira/browse/HDFS-385
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Fix For: 0.21.0
>
> Attachments: BlockPlacementPluggable.txt,
> BlockPlacementPluggable2.txt, BlockPlacementPluggable3.txt,
> BlockPlacementPluggable4.txt, BlockPlacementPluggable4.txt
>
>
> The current HDFS code typically places one replica on local rack, the second
> replica on remote random rack and the third replica on a random node of that
> remote rack. This algorithm is baked in the NameNode's code. It would be nice
> to make the block placement algorithm a pluggable interface. This will allow
> experimentation of different placement algorithms based on workloads,
> availability guarantees and failure models.
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